In general, an image forming apparatus includes an optical scanning unit. In the optical scanning unit, a light beam emitted by a light source may enter a rotatable deflector via a lens. Then, the light beam deflected by the rotatable deflector may be guided to an image-carrying member such as photoconductor to scan a surface of the image-carrying member to form a latent image on the image-carrying member.
For example, such optical writing unit may include a light source, a collimate lens, a cylindrical lens, a polygon mirror (as rotatable deflector), and other mirrors to guide a light beam from the light source to the image-carrying member.
In such optical writing unit, if a reflection face of the polygon mirror may be slanted from an optimal angle (i.e., mirror face has a tangle error), or if an axis of the polygon mirror may be slanted from an optimal angle due to assembly error, light beams may scan the image-carrying member with an uneven pitch relative to each other, or light beams may not be focused on a optimal position on the image-carrying member.
If such phenomenon may occur, a resultant image to be produced on a recording medium may have a lower image quality.
The cylindrical lens may be provided in the optical writing unit to reduce the above-mentioned drawbacks. In general, the cylindrical lens may be disposed between the light source and polygon mirror used as rotatable deflector.
A light reference-axis of the cylindrical lens may be defined between a light emitting point of the light source and a given reflection point of the polygon mirror used as rotatable deflector.
A related art image forming apparatus may include an optical writing unit having a moving unit for moving a cylindrical lens to adjust a reference-axis direction of cylindrical lens.
In such related art, the cylindrical lens may be moved by a driver (e.g. motor) to adjust a reference-axis direction of the cylindrical lens.
Accordingly, such related art may need a driver, driving-force transmission mechanism, and a driving mechanism controller, for example, by which such related art may have a complex configuration and need a space for allocating such devices. Such a configuration may not be favorable from a viewpoint of miniaturization of image forming apparatus.
Another related art image forming apparatus may include an optical writing unit having another configuration for moving a cylindrical lens in its reference-axis direction.
Such optical writing unit may include a lens holder, which holds the cylindrical lens, and a housing having a support face on which the lens holder is placed.
The lens holder may be movable on the support face in a direction parallel to a reference-axis direction of the cylindrical lens.
The support face may include a guide member thereon to guide a movement of the lens holder in the reference-axis direction of the cylindrical lens.
The lens holder may have an adjustment hole, which has a substantially rectangular shape formed along the support face and parallel to the reference-axis direction.
A screw may be inserted through the adjustment hole and then may be engaged with a screw hole provided on the housing used as support member.
In such optical writing unit, the screw may be loosened when adjusting a position of the cylindrical lens.
Specifically, under such screw-loosened condition, the lens holder may be moved in the reference-axis direction by a force applied from a hand of maintenance person to adjust a position of the lens holder.
After adjusting a position of the lens holder at an appropriate position, the screw may be tightened to fix the cylindrical lens at such appropriate position.
Such optical writing unit may not need a driver, driving-force transmission mechanism, and a driving mechanism controller to adjust a position of the cylindrical lens, by which such another related art may not need a complex configuration and a space for allocating such devices.
Another background art image forming apparatus may include another optical writing unit having another configuration for moving a cylindrical lens in its reference-axis direction.
Such optical writing unit may include a lens holder for holding a cylindrical lens, and a housing (used as support member) having a support face having a guide hole.
The guide hole may have a substantially rectangular shape formed along the support face and parallel to the reference-axis direction.
The lens holder has a protruded portion to be snap-fitted to the guide hole, and the lens holder may be moveable on the support face in the reference-axis direction of the cylindrical lens when the protruded portion of lens holder moves in the guide hole.
Furthermore, the housing may have a long-shaped hole aligned in the reference-axis direction of the cylindrical lens.
When the lens holder is placed on the housing, a projection portion of the lens holder may be exposed to an outside of the housing. In other words, the projection of the lens holder may pass though the long-shaped hole, and an exposed portion of the lens holder may be used to move the lens holder in the reference-axis direction of the cylindrical lens.
Specifically, a maintenance person may grab the exposed portion of the lens holder and move the lens holder along the long-shaped hole by applying a hand force, by which a position of the cylindrical lens may be adjusted.
Such optical writing unit may further include another configuration having an eccentric cam for moving the cylindrical lens in the reference-axis direction with a hand force of maintenance person.
In this art, the lens holder may have a long-shaped hole formed in a direction perpendicular to a reference-axis direction.
The eccentric cam may include a circular base, a center-axis shaft, and an eccentric-axis shaft, for example.
The center-axis shaft may extend in a first direction from the circular base and may be aligned on a rotational axis of the circular base.
The eccentric-axis shaft may extend in a second direction from the circular base deviated from a rotational axis of the circular base. The first direction and second direction may be set to an opposite direction each other, for example.
The center-axis shaft of eccentric cam may be inserted in a bearing hole of the housing and some part of the center-axis shaft may be exposed to an outside of the housing.
The eccentric-axis shaft of eccentric cam may be inserted in the long-shaped hole of the lens holder.
A maintenance person can grab an exposed portion of the center-axis shaft to rotate the eccentric cam with a hand force.
With such configuration, the lens holder may be moved in its reference-axis direction while the protruded portion of the lens holder may be guided in the guide hole of the housing.
Accordingly, a maintenance person may adjust a position of the cylindrical lens in its reference-axis direction with a hand force.
Such optical writing unit may not need a driver, driving-force transmission mechanism, and a driving mechanism controller to adjust a position of the cylindrical lens, by which such background art may not need a complex configuration and a space for allocating such devices.
However, the above-mentioned optical writing unit may have a lower working efficiency when adjusting a position of the cylindrical lens by a maintenance person. Hereinafter, such drawback may be explained.
In general, when adjusting a position of the cylindrical lens in its reference-axis direction, an optical writing unit may be placed on a platform of an adjustment machine, wherein a posture or orientation of the optical writing unit on the platform may be set substantially similar to a posture or orientation of the optical writing unit in an image forming apparatus.
Then, a light-receiving device such as CCD (charge coupled device) may be placed on a given position of the adjustment machine, wherein the given position may correspond to a position of a surface of image-carrying member (or photoconductor) when the optical writing unit is placed in the image forming apparatus. A number of light-receiving devices may be set to one or two, for example.
Then, the optical writing unit is activated, and the light-receiving device may detect a light beam scanning the image-carrying member in an axis direction of the image-carrying member.
Then, such detected result may be displayed on a display unit as lens-position-adjustment information. A maintenance person may check or look up such information to adjust a position of the cylindrical lens.
In such optical writing unit, when a maintenance person grabs the lens holder by hand to move the lens holder, the hand of maintenance person may block a path of incident light or outgoing light of the cylindrical lens.
In such configuration, the maintenance person may adjust a position of the cylindrical lens as below.
At first, the maintenance person may move the lens holder with a hand. Then, the hand is set aside from the optical writing unit so that the light-receiving device can detect a light beam.
Then, by checking or looking up lens-position-adjustment information prepared from a detection result detected by the light-receiving device, the maintenance person may move the lens holder by hand again to adjust a position of the cylindrical lens.
The maintenance person may repeat the above-mentioned processes to find an appropriate position of the cylindrical lens.
Such process may not be convenient for the maintenance person because the maintenance person may have to stop a movement of the lens holder to check or look up the lens-position-adjustment information and then restart a movement of the lens holder.
Accordingly, the maintenance person may feel an inconvenience for conducting such above-mentioned processes.
In case of background art image forming apparatus, a maintenance person can move the lens holder by grabbing the exposed portion of center-axis shaft by hand, which may be exposed to an outside of the housing.
Accordingly, a hand of maintenance person may not block an incident light or outgoing light of the cylindrical lens when adjusting a position of cylindrical lens.
Under such configuration, the maintenance person may adjust a position of the cylindrical lens as below.
The maintenance person may move the lens holder with a hand while checking or looking up lens-position-adjustment information prepared from a detection result detected by the light-receiving device to find an appropriate position of the cylindrical lens.
Accordingly, in the background art image forming apparatus, the maintenance person may adjust a position of the cylindrical lens in the optical writing unit easier compared to the above-mentioned optical writing unit in the related art image forming apparatus.
However, the optical writing unit in the background art image forming apparatus may be disposed under an image-carrying member (or photoconductor) when the optical writing unit is installed in the image forming apparatus, wherein the optical writing unit emits a light beam (or scanning light beam) in an upward direction.
Accordingly, such optical writing unit may be placed on a platform of an adjustment machine with a posture or orientation, which may be substantially similar to a posture or orientation of the optical writing unit, which is installed in the image forming apparatus.
Therefore, when the optical writing unit is placed on the platform of the adjustment machine, the exposed portion of the center-axis shaft, exposed to an outside of the housing, may face a downside in a vertical direction.
Under such configuration, the maintenance person may have to put a hand from a downside of the platform when adjusting a position of the cylindrical lens.
Accordingly, the maintenance person may have to move the exposed portion of the center-axis shaft from downside of the optical writing unit, placed on the platform of the adjustment machine.
The maintenance person may feel uncomfortable for such adjustment work compared to an adjustment work conducted from an upper side of the optical writing unit placed on the platform of the adjustment machine. Such uncomfortable situation may be undesirable from a viewpoint of a positioning the cylindrical lens with a higher precision.
Positioning of cylindrical lens in its reference-axis direction may need a higher precision to enhance or maintain an image quality to be produced by an image forming apparatus. Therefore, it has been desired that a maintenance person can conduct such adjustment work in a precise manner by a hand with a simplified manner.